A vesting cliff is the minimum time period a person must remain with a company before any granted equity vests. Leaving before the cliff date forfeits the entire grant. The startup standard is a one-year cliff inside a four-year vesting schedule, applied to both employees and founders, and built into virtually every cap-table-tool default (Carta, Pulley, AngelList Equity).
In practice, the one-year cliff works as a binary test. An employee granted 48,000 options on a four-year monthly schedule vests zero options for the first 365 days. On day 366, exactly 12,000 options (25% of the grant) vest at once. From then on, the remaining 36,000 vest at 1,000 per month for three years. The cliff exists to protect the company and the ca...